Rod-reinforced cushion beam

ABSTRACT

A rod-reinforced cushion beam includes a rigid frame having a spaced plurality of main rod members and a longitudinally paced plurality of connecting elements; and a plastic body encapsulating and substantially solidly filling the frame. A preferred embodiment has least 90 percent by weight of the plastic body in a main polymeric component of linear low density polyethylene, and an additive component that does not contain filler material. Also disclosed is a method for forming a rod-reinforced cushion beam.

RELATED APPLICATION

[0001] This application is a continuation-in-part of application Ser.No. 10/278,754, filed on Oct. 22, 2002, now U.S. Pat. No. ______, whichis incorporated herein by this reference.

BACKGROUND

[0002] The present invention relates to elongated structural memberssuch as pilings, columns, wales, planks, and beams, particularly forused in marine environments, and methods for making such members.

[0003] Concrete, steel, and wood are conventionally used for pilings,telephone poles, beams and the like. However, each of these materialshas disadvantages. Concrete and steel pilings are heavy and awkward tomaneuver. Neither concrete nor steel pilings make good fender pilingsbecause neither is “forgiving” when impacted. Under impact steel bendsand buckles and concrete shatters. Both concrete and steel pilings areexpensive to repair. Furthermore, steel, either standing alone or as areinforcement in porous concrete, is subject to corrosion.

[0004] Wood pilings, planks, and beams are plagued by wear and tear and,particularly in marine environments such as in piers and ship moorings,are attacked by wood-boring marine organisms. Wood pilings, wales andplanks are typically treated with creosote, but even this material canbe ineffective against modern marine borers. These marine borers canonly be stopped by wrapping the wood pilings in plastic coverings.However, these plastic coverings cannot withstand much wear and tear,especially abrasion from normal vessel contact. So in addition to a thinplastic wrap, wooden fender piles and planks often require thick plasticwrappings, which are expensive to put in place, being also subject toseparation.

[0005] Composite pilings are also known, being disclosed for example inU.S. Pat. No. 5,180,531 to Borzakian, that document being incorporatedherein by this reference. The '531 patent discloses a plastic pipehaving an inner pipe core or mandrel being 6 inches or less in diameter,and a substantially homogenous coating being at least two inches thick.The thick plastic coating provides the bulk of the mechanical strength,being formulated with a desired combination of flexibility, brittleness,and impact resistance for use as pilings including fender pilings ofdocks, telephone poles, light standards, etc.

[0006] U.S. Pat. No. 5,766,711 to Barmakian, which is incorporatedherein by this reference, discloses a composite camel structureincluding a pipe mandrel and a thermally bonded plastic cushionsurrounding the mandrel. A mold having the mandrel centered therein isfilled with molten plastic, the plastic being cooled and solidified byfeeding water into the mandrel for progressively solidifying the cushionmember along mandrel for producing a thermal bond without excessivetensile strain in the plastic material, thereby to achieve asubstantially unbroken outside surface.

[0007] U.S. Pat. No. 6,244,014 to Barmakian, which is incorporatedherein by this reference, discloses a composite piling having a weldedcage including a circular array of parallel spaced main rod members thatare welded about a helically formed secondary rod member, the cage beingencapsulated in a plastic body.

[0008] U.S. Pat. No. 6,412,431 to Barmakian et al., which is alsoincorporated herein by this reference, discloses a composite fenderhaving a cage frame encapsulated in a plastic body, the cage framehaving an attachment structure connected to plural spaced apartlocations of the frame.

[0009] Notwithstanding the above, it is believed that there is a needfor further improvements in structural components to be used as beams inmoorings, piers, and the like that are contemplated to be used in marineenvironments, that such components have high bending strength and highresistance to impact loading, and that they have long life, are easilyinstalled, environmentally sound, and durable in use.

SUMMARY

[0010] The present invention meets this need by providing a reinforcedcushion beam of high bending strength, being particularly suitable for avariety of marine applications. In one aspect of the invention, an acomposite beam includes a frame having plural longitudinal main rodmembers at least three of which are spaced in different directionsrelative to a longitudinal axis of the frame, and a plurality oftransverse elements each rigidly connecting a spaced pair of the mainrod members, at least three of the main rod members being connected toat least two others of the main rod members by at least some of thetransverse elements; and a resilient plastic body encapsulating theframe and having a nominal cross-sectional area of at least 50 squareinches. As used herein, the term “nominal cross-sectional area” meansoverall (inclusive of the frame) cross-sectional area when thecross-sectional area of the body member is uniform, and averagecross-sectional area when the cross-sectional area of the body member isnon-uniform, such as tapering. The plastic body can form an elongatecushion surface, the cage frame being spaced from the cushion surface bypreferably not less than 10 percent of an overall thickness of the beambetween the cushion surface and an opposite surface of the beam.

[0011] At least some of the transverse elements can be shear panels. Theshear panels can include respective laterally spaced first and secondsets of longitudinally spaced shear panels, the panels of each setjoining a pair of the main rod members. The sets of shear panels can beconnected between respective first and second pairs of the main rodmembers. The main rod members can include respective third and fourthpairs of the main rod members, the first set of shear panels also beingconnected between the third pair of main rod members opposite the rodmembers of the first pair, the second set also being connected betweenthe fourth pair of main rod members opposite the rod members of thesecond pair. Also, or alternatively, at least some of the shear panelscan have openings and/or notches formed therein, the body havingportions external to the cage frame being integrally joined through theopenings and/or notches with portions of the body within the frame forenhanced structural integrity of the body.

[0012] Preferably, the main rod members and the transverse elements forma cage truss, wherein the term “cage-truss” means a rigid structurehaving a spaced array of elements in plural planes, the elements beingstrained primarily in tension and compression in response to bending andshear loading of the structure as a whole.

[0013] The main rod members and the transverse rod segments are eachpreferably spaced at least 0.5 inch within an outside contour of theplastic body for resistance to penetration by abrasion.

[0014] The main rod members are preferably selected from the groupconsisting of formed steel reinforcing bars, formed nickel alloyreinforcing bars, fiberglass reinforcing bars, and carbon fiberreinforcing bars, and at least some of the transverse elements can beselected from the group consisting of formed steel reinforcing bars,formed nickel alloy reinforcing bars, fiberglass reinforcing bars,carbon fiber reinforcing bars, plastic dowels, wooden dowels, steelplates, and fiberglass panels.

[0015] The main rod members can have a nominal diameter of betweenapproximately 2 percent and approximately 6 percent of a nominal outsidecircumference of the plastic body. As used herein, the term “nominaloutside circumference” of the plastic body means the overallcircumference when the cross-sectional area of the body member isuniform, and average circumference when the cross-sectional area of thebody member is non-uniform, such as tapering.

[0016] Preferably the plastic body sealingly surrounds the cage frame,having a thickness of not less than approximately 4 percent of theoutside circumference of the plastic body over each of the main rodmembers and the transverse elements. The outside circumference of theplastic body can be approximately 48 inches, the diameter of the mainrod members being approximately 1.25 inch. The plastic body can berectangular or square in cross-section.

[0017] The plastic body preferably substantially fills the spaceoccupied by the cage frame. The plastic body can consist of a mainpolymeric component and an additive component, the main polymericcomponent consisting of low-density polyethylene of which at least 60percent is linear low density polyethylene, the additive componentincluding an effective amount of an ultraviolet inhibitor.

[0018] Preferably the composite beam also includes an attachmentstructure defining attachment elements that are connected to pluralspaced locations of the frame. Also, a plurality of the composite beamscan be assembled to stationary structure to form an installed fenderassembly.

[0019] In another aspect of the invention, a method for forming acomposite beam includes:

[0020] (a) providing a plurality of elongate main rod members;

[0021] (b) providing a plurality of transverse elements;

[0022] (c) rigidly securing opposite portions of each of the transverseelements between a laterally spaced pair of the main rod members suchthat each of at least three of the main rod members have pluralities ofthe transverse rod segments laterally projecting in at least twodirections diverging from the main rod members to form a cage frame; and

[0023] (d) encapsulating the cage frame in a plastic body.

[0024] The rigidly securing is preferably further such that at leastsome of the transverse elements are rod members oriented diagonally forloading the main rod members and the transverse elements that are inplanes of the diagonally oriented rod segments primarily in tension andcompression in response to bending and shear loading of the resultingcage truss. The securing can be by welding and/or by forming reinforcedjoints of epoxy resin. The rigidly securing can also, or in thealternative, be of shear panels forming at least some of the transverseelements, the main rod members being strained primarily in tension andcompression in response to bending and shear loading of the resultingcage truss.

[0025] In a further aspect, a method for forming a composite beamincludes:

[0026] (a) rigidly securing a spaced plurality of main rod members toopposite edge regions of a first longitudinally spaced array of shearpanels to form a first frame portion;

[0027] (b) rigidly securing a spaced plurality of main rod members toopposite edge regions of a second longitudinally spaced array of shearpanels to form a second truss;

[0028] (c) locating the first and second trusses in laterally spacedrelation;

[0029] (d) rigidly securing a longitudinal array of lateral elementsbetween the first and second trusses to form a cage frame; and

[0030] (e) encapsulating the bonded cage frame in a plastic body.

[0031] The encapsulating can include:

[0032] (a) providing an injection mold having an elongate cylindricalcavity;

[0033] (b) loading the mold with the cage frame;

[0034] (c) centering the welded cage frame within the mold;

[0035] (d) injecting a polymeric composition into the mold therebycovering the cage frame; and

[0036] (e) cooling the mold to form the structural plastic member.

[0037] Preferably the injecting includes formulating the polymericcomposition to consist of low density polyethylene, at least 60 percentof the polymeric composition being linear low-density polyethylene forresisting cracking of the material. The method can also include bondinga plurality of fastener attachments to the cage frame.

DRAWINGS

[0038] These and other features, aspects, and advantages of the presentinvention will become better understood with reference to the followingdescription, appended claims, and accompanying drawings, where:

[0039]FIG. 1 is a fragmentary sectional side view of a reinforcedcushion beam structure according to the present invention, the sectionbeing taken on line 1-1 of FIG. 2;

[0040]FIG. 2 is a fragmentary sectional top view of the beam structureof FIG. 1 taken on line 2-2 therein;

[0041]FIG. 3 is an oblique perspective view of a cage truss portion ofthe beam structure of FIG. 1;

[0042]FIG. 4 is a lateral sectional view of a the beam structure of FIG.1;

[0043]FIG. 5 is a flow chart for a process of forming the pilingstructure of FIG. 1;

[0044]FIG. 6 is a fragmentary sectional side view showing the beamstructure having an alternative configuration of the cage truss of FIG.3;

[0045]FIG. 7 is an oblique perspective view showing an anotheralternative configuration of the cage truss of FIG. 3;

[0046]FIG. 8 is a lateral sectional view as in FIG. 4, showing analternative configuration of the beam structure of FIG. 1; and

[0047]FIG. 9 is an end elevational view of a fending panel incorporatingbeam structures of the present invention and fastened on stationarystructure;

[0048]FIG. 10 is a front elevational view of the fending panel of FIG.9; and

[0049]FIG. 11 is an oblique perspective view showing a cage frame asanother alternative configuration of the cage truss of FIG. 3;

[0050]FIG. 12 is a side view as in FIG. 6, showing a further alternativeconfiguration of the cage truss of FIG. 3;

[0051]FIG. 13 is a lateral sectional view of the cage truss of FIG. 12;and

[0052]FIG. 14 is a side view showing an alternative configuration of thecage truss of FIG. 12.

DESCRIPTION

[0053] The present invention provides a novel reinforced plastic cushionbeam that is particularly effective as a sheathing plank, wale, or otherstructural element of a wharf facility. With reference to FIGS. 1-4 ofthe drawings, a cushion beam 10 according to the present inventionincludes an elongate cage structure 11 in the form of a cage truss 12,and a resilient plastic material forming a cylindrical plastic body 14and encapsulating the cage truss 12. As best shown in FIGS. 1, 2, and 4,an exemplary configuration of the cushion beam 10 is generallyrectangular in cross-section, having an outside width W and an outsidedepth D which can be the same as the width W, and an overall length Lthat can be from approximately 10 feet to approximately 60 feet, or evenlonger. In one specific exemplary configuration the width W and thedepth D are each approximately 12 inches. Also, the plastic body 14 asshown in the drawings is cylindrical, having a uniform cross-sectionbetween opposite end extremities of the cushion beam 10. As used herein,the term “cylindrical” means having a surface that is generated by astraight line that moves parallel to a fixed line. Thus, although thebody 14 is shown in the drawings as rectangularly cylindrical, othercross-sectional shapes such as circular, elliptical, polygonal, androunded polygonal are also contemplated within the scope of the presentinvention. Moreover, it is also contemplated that the cushion beam 10can be curved and/or have a non-uniform cross-section within the scopeof the present invention.

[0054] The cage truss 12 includes a plurality of longitudinal main rodmembers 16 that are rigidly interconnected by transverse elements 17that can include a multiplicity of transverse rod segments 18, oppositeend portions of each segment 18 being connected between a pair of themain rod segments 16. As best shown in FIG. 4, the main rod segments 16are spaced laterally in plural directions relative to a longitudinalaxis 19 of the truss 12, with each of the main rod members havingtransverse rod segments projecting in plural directions havingcomponents perpendicular to the longitudinal axis 19 (the plane of FIG.4 being generally perpendicular to the longitudinal axis 19). Preferablyat least some of the transverse rod segments 18 are diagonal segments20, as shown in FIGS. 1 and 3, so as to impart primarily tension andcompression loads on the main rod members 16 and the transverse rodsegments 18 in response to bending and shear loading of the cage truss12 as a whole. In the exemplary configuration shown in FIGS. 1-4, thecage truss 12 is adapted for transmitting bending and shear loadingprimarily in the plane of FIG. 1. In particular, the cage truss 12 hasat least one additional transverse rod segment 18 connected in coplanarrelation proximate each end portion of the diagonal rod segments 20. Asshown in FIG. 1, there are two such additional coplanar transverse rodsegments 18 proximate each diagonal rod end extremity, (one beinganother of the diagonal rod segments 20, the other being a lateral rodsegment, designated column rod segment 22) except at opposite ends ofthe cage truss 12, where there is one such additional transverse segment(a column rod segment 22) at each connection location. Other lateral rodsegments, designated tie rod segments 24, extend perpendicularly betweenopposite sides of the cage truss 12 as best shown in FIGS. 2-4.

[0055] In another aspect, the cage truss 12 includes a spaced pair ofgenerally planar truss units 26 that are connected in generallyparallel-spaced relation by the tie rod segments 24. In one preferredform, the cage truss 12 is a weldment of steel reinforcing bars havingribbed contours as indicated in FIG. 4 for enhanced gripping andadhesion by the plastic body 14, weldable steel reinforcing bars (ASTM706) being commercially available from a variety of sources. Moreparticularly, a first truss unit 26A includes a first pair (16A and 16B)of the main rod members connected proximate opposite ends of one subset18A of the transverse rod segments 18, and a second pair 16C and 16D ofthe main rod members connected on opposite ends of another subset 18B ofthe transverse rod segments 18, one subset 24A of the tie rod segments24 being connected between the rod members 16A and 16C, another subset24B of the tie rod segments 24 being connected between the rod members16B and 16D as best shown in FIG. 4. Additionally, a third pair (16E and16F) of the main rod members are connected proximate opposite ends ofthe first transverse rod subset 18A opposite the first pair 16A and 16B,and a fourth pair (16G and 16H) of the main rod members connectedproximate opposite ends of the second transverse subset 18B. Thus eachof the truss units 26A and 26B is laterally symmetrical on oppositesides of a (typically planar) surface defined by the respectivetransverse rod segment subsets 18A and 18B for maximum resistance todeflection from loads applied (at least locally) coplanar with thatsurface. It will be understood that for additional lateral stabilityand/or for resistance to loading in directions having componentsparallel to the tie rod segments 24, the cage truss 12 can includeadditional diagonal rod segments 20 in other orientations (not shown),such as diagonally between pairs of the tie rod segments 24 of therespective subsets 24A and 24B.

[0056] As shown in FIG. 2, the cage frame 12 also includes a pluralityof fastener attachments 30 for mounting the cushion beam 10 to otherstructure and/or for mounting other structural elements to be supportedby the cushion beam 10. As shown in FIG. 1, a first plurality of theattachments, designated threaded sleeves 32, is welded to the cage frame10 and forming a rigidly connected component thereof at spaced locationsdefining a first mounting surface 33. A second plurality of attachments,designated floating sleeve 34, are imbedded proximate a second mountingsurface 35 the resilient body 14 so as to form a cushioned mounting forother supported structure as described below in connection with FIGS. 9and 10.

[0057] An important feature of the present invention is a formulation ofpolymeric material that is suitable for encapsulating the cage truss 12and that does not form voids and cracks due to tensile thermal strainsbeing generated during solidification. This problem is exacerbated bythe absence of a tubular mandrel that can receive cooling water asdisclosed in the camel structure of the above-referenced '711 patent. Ithas been discovered that a particularly suitable composition for formingthe plastic body 14 as an uninterrupted covering of the cage truss 12 isa main first quantity of low density polyethylene of which at least 60percent and preferably 65 percent is linear low-density polyethylene(LLDPE), the balance being regular low-density polyethylene (LDPE), anda process additive second quantity including an effective amount of UVinhibitor, the composition not having any significant volume of fillermaterial such as calcium carbonate. Preferably, the first quantity is atleast 90 percent of the total volume of the plastic body 14,approximately 5 percent of the total volume being a mixture of coloring,foaming agent, and UV inhibitor. Preferably the composition issubstantially free (not more than 5 percent) of high densitypolyethylene.

[0058] Thus the composition of the cushion member 14 has polymericelements being preferably exclusively polyethylene as described above(substantially all being of low-density and mainly linear low-density),together with process additives as described below. As used herein, theterm “process additive” means a substance for enhancing the propertiesof the polymeric elements, and does not include filler material such ascalcium carbonate. The composition preferably contains a processadditive which can be a foaming or blowing agent in an amount of up toabout 0.9% by weight to insure than when the plastic body 14 is made byextruding the plastic composition into a mold, the mold is completelyfilled. The foaming agent can be a chemical blowing agent such asazodicarbonamide. A suitable chemical blowing agent is available fromUniroyal of Middlebury, Conn., under the trade name Celogen AZ 130.

[0059] Other process additives of the composition can include a couplingagent, preferably a silane, for improved bonding between the plasticbody 14 and the cage truss 12.

[0060] The plastic composition can also include a fungicide, typicallyin an amount of about 0.25% by weight, and an emulsifier, in an amountof from about 0.1% to 0.3% by weight. The use of emulsifier improvessurface appearance of the product.

[0061] The composition can also contain a carbon black, generally afurnace black, as a colorant, to improve the physical properties, and asa UV stabilizer. The amount of carbon black used is generally about 2.5%by weight.

[0062] A mold apparatus (not shown) for encapsulating the cage truss 12to form the plastic body 14 of the cushion beam 10 includes a moldassembly and a conventional extruder press, including one or moreflanged tubular mold segments as further described in theabove-referenced '014 patent, but with the cross-sectional shape of themold segments conforming to the cross-sectional shape of the body 14,with appropriate allowances for shrinkage as further described in the'014 patent.

[0063] As further described in the '014 patent, the cage truss 12centered within a main cavity of the mold assembly, being supported by aplurality of projections 20, and/or by fasteners temporarily engagingone or more of the fastener attachments 30, or by centering screws asdisclosed in the above-referenced '711 patent. Alternative moldconstruction is also described in the above-referenced '431 patent.

[0064] With further reference to FIG. 5, a process 100 for forming thecushion beam 10 includes providing the main and transverse rods 16 and18 in a provide rods step 102, a weld trusses step 104 in which thetruss units 26A and 26 B are assembled and welded, the truss units 26being joined in spaced relation in a weld cage step 105. Then, in a loadmold step 106, the cage truss 12 is placed within the mold assembly andanchored in registration therewith. The mold is closed in a close moldstep 108 and, optionally in an incline mold step 109, the mold assemblyis propped up on a suitable support for elevating an exhaust ventthereof.

[0065] Next, the material of the plastic body 14 is fed into the maincavity in an inject body step 110. Then in a cooling step 112, the moldassembly with its contents is submerged in cooling water for solidifyingthe material of the plastic body 14, after which the assembly 42 isremoved from the water (step 114), the mold is opened (step 116), andthe substantially complete cushion beam 10 is withdrawn (step 118).Further details of this process are described in the above-referenced'014 and '431 patents.

[0066] With further reference to FIG. 6, an alternative configuration ofthe cushion beam, designated 10′, a counterpart of the cage truss,designated 12′, has a single formed rod member, designated 20′,substituted for the diagonal rod segments of each of the truss units 26Aand 26B. As also shown in FIG. 6, some of the other transverse rodsegments of the configuration of FIGS. 1-4 are omitted, namely all butthe endmost column rod segments 22 and every other one of the tie rodsegments 24. With further reference to FIG. 7, a counterpart of the cagetruss 12′, designated 12″, has the members omitted from the truss 12′restored, the restored column rod segments, designated 22′, beingforeshortened and abutting formed portions of the diagonal rod member20′.

[0067] With further reference to FIG. 8, another alternativeconfiguration of the cushion beam, designated 12″, has a non-rectangularcross-sectional configuration, and a counterpart of the cage truss,designated 12′″, is non-rectangular. In particular, counterparts of thefirst and second truss units, respectively designated 26A′ and 26B′, areinclined laterally, counterparts of the main rod members 16A and 16Dbeing shared by the truss units 26A′ and 26B′, the tie rod segments 24of the first subset 24A being omitted. Thus the first truss unit 26A′includes counterparts of the main rod members 16A, 16B, 16C, and 16F,the second truss unit 26B including counterparts of the main rod members16A, 16C, 16D, and 16H, there being no counterparts of the main rodmembers 16E and 16G. Also, the alignment of locally proximate pairs ofthe main rod members, namely 16A and 16C, 16B and 16F, and 16D and 16H,are oriented in facing relation to the longitudinal axis 19 forsimultaneous engagement at opposite sides of the transverse rod segmentsthat project in respective acutely divergent planes, which in theexemplary configuration shown in FIG. 8 form an equilateral triangle.Further, counterparts of the threaded sleeves 32 are located proximate acounterpart of the first mounting surface 32 and proximate opposite endextremities of the tie rod segments 24, being welded thereto and toadjacent ones of the main rod segments 16 as well as transverse rodsegments 18 of the first and second truss units 26A′ and 26B′. As yetfurther shown in FIG. 8, one or more counterparts of the floatingsleeve, designated 34′, is located proximate a second mounting surfaceand in spaced relation proximate the main rod members 16A and 16C. Oneor more formed counterparts of the anchor member, designated 36′, hasopposite ends welded to opposite sides of the floating sleeve 34′, theanchor members 36′ together with the floating sleeve 34′ enclosing themain rod members 16A and 16C in spaced relation such that the floatingsleeve 34′ is resiliently supported relative to the cage truss 12′″.

[0068] With further reference to FIGS. 9 and 10, a fending panelassembly 40 includes at least one cushion beam, three vertically spacedand transversely mounted beams 10″ being shown, and at least one panelmember 42, a plurality of panel members 42 being shown connected betweenthe cushion beams 10″. More particularly, the first mounting surfaces 34of the beams 10″ are oriented vertically, being fastened against astationary structure 43 by a plurality of first fasteners 44 that engagerespective ones of the fastener attachments 30. The panel member 42 isfastened against the second mounting surface 35 by a plurality of secondfasteners 46 that engage the floating sleeves 34 to form a fenderassembly for cushioning moored ships. A plurality of sheathing planks 48are also shown fastened in generally coplanar relation to the panelmembers 42 in FIG. 9, it being understood that any combination ofpanel(s) and/or plank(s) (or other structural elements) can be supportedby one or more of the cushion beams 10, 10′ and/or 10″. Moreover, thesheathing planks can be additional counterparts of the cushion beams,such as the cushion beams 10 and 10′.

[0069] In some military based naval applications, it is undesirable fora marine-exposed structure to be electro-magnetically sensitive. In suchapplications the cage truss 12 can be formed with non-magneticmaterials, such as nickel reinforcing bar (formed of acorrosion-resistant steel alloy), which is available from MMFX SteelCorp. of America, Charlotte, N.C. Another suitable material iscarbon-reinforced plastic bar, available from Aero Space CompositeProducts of San Leandro, Calif. The cage truss 12 can also be developedby using fiberglass reinforcing rods, with reinforced epoxy joints atpoints of contact between the main rods 12 and the various transverserod segments 18 and/or diagonal rod segments 20. Additional suitablematerials include Nylon Reinforcement, available from McMasters Co. ofLos Angeles, Calif., plastic dowels, also available from McMasters, andwooden dowels, which are available from typical lumber yards.

[0070] With further reference to FIG. 11, certain of the non-metallicmaterials, most particularly the fiberglass reinforcing rods, aresuitably joined with epoxy resin and locally applied layers or otherquantities of fiberglass reinforcement to form rigidly bonded joints.When this form of construction is utilized it is often possible todispense with the diagonal rod segments 20 in that the resulting frame,designated 12″″, imparts a desired amount or resistance to bending. Asshown in FIG. 11, one or more of the column rod segments 22 and the tierod segments 24 are rigidly bonded to the main rod members 16 by epoxyresin 52 having one or more layers of fiberglass fabric 54 therein.

[0071] With further reference to FIGS. 12-14, another alternativeconfiguration of the cushion beam, designated 60, has an alternativeconfiguration of the cage structure 11 that incorporates shear panels assome or all of the transverse elements 17 of the cage truss 12, in placeof (or in addition to) some or all of the diagonal rod segments 20 (orthe diagonal rods 20′ of FIG. 6) and column rod segments 22 (and/or 22′of FIG. 7) as described herein. As shown in FIGS. 12 and 13, one suchcage structure, designated cage frame 62, has a spaced plurality ofrectangular shear panels 64 joined along opposite edges thereof to aspaced pair of the main rod members 16. It will be understood thatalthough the term “cage truss” as applied to the cage structures 11 ofFIGS. 1-11 does not strictly apply in that the shear panels 64 (andportions of the main rod members 16 between the shear panels) have shearloading, the deflection of the cage frame 62 that is attributable toshear loading of the main rod members is much less than would be presentin the cage truss 12 of FIG. 1 if the diagonal rod segments 20 wereomitted, because the portions of the main rod members 16 that aresubject to shear loading (and consequent strain) make up only a smallproportion of the length of the cage frame 62.

[0072] In the exemplary configuration of FIGS. 12 and 13, there are twosets of the shear panels 64, designated 64A and 64B in FIG. 13, that aresandwiched between pairs of the main rod members, the panels 64A beingwelded along one edge between the main rod members 16A and 16E, andalong the opposite edge between the main rod members 16B and 16F.Similarly, the other panels 64B are welded along one edge between themain rod members 16C and 16G, and along the opposite edge between themain rod members 16D and 16H as shown in FIG. 13. The tie rod segments24 (24A and 24B) are located within gaps between the shear panels 64 asshown in FIG. 12. It is not necessary that there be tie rod segments ineach of the gaps, depending on the size of the panels 64, the gapshaving a primary purpose of providing structural integrity of theplastic body 14 within and outside of the cage frame 62 in that thematerial of the body 14 extends through passages formed by the gaps. Thegaps also result in a reduction in the total weight of the shear panels64, which are preferably provided in a thickness sufficient to carrycompressive loading between the main rod members (16A and 16B, forexample) at opposite edges of the panels 64. Thus the shear panels 64are substituted for both the diagonal rod segments 20 and the column rodsegments 22 of FIG. 1. In a counterpart of the exemplary 12-inch by12-inch beam 10 described above, the shear panels 64 can be provided asapproximately ⅛ inch thick mild steel plates measuring 9 ⅜ inch in adirection perpendicular to the main rods 16 (for extending just beyondthe midpoints of the rods to which they are welded), and from 6 to 8inches in a direction parallel to the main rods, the spacing between thepanels 64 being from approximately 1 inch to approximately 3 inches. Theshear panels 64 can also be formed of nonmetallic materials such asfiberglass, being suitably bonded to the main rod members 16,substituting for some or all of the transverse rod elements (the columnrod segments 22 and the tie rod segments 24) in the cage truss 12″″ ofFIG. 11.

[0073] With particular reference to FIG. 14, an alternativeconfiguration of the cage frame, designated 62′, has one or morecounterparts of shear panels, designated 64′, in extended lengths andhaving notches and/or openings therein for clearing the tie rod segments24 and/or providing passages connecting outer and inner portions of theplastic body 14. In the exemplary configuration of FIG. 14, the shearpanel 64′ extends substantially the full length of the cage frame 64,having notches 66 formed along opposite edges thereof for clearing thetie rods 24, and having a spaced plurality of openings 68 that areconfigured for maintaining shear and transverse compression strengthwhile robustly connecting inner and outer portions of the plastic bodyand reducing the overall weight of the cage frame 62′.

[0074] The cushion beam 10 (as well as the alternatively configuredbeams 10′, 10″, 60, 60′, and 60″) of the present invention is immune tomarine borer attack, and thus requires no further protection, such ascreosote or plastic sheathing, being practically maintenance free. Thecushion beam 10 is abrasion resistant, and thus has excellenteffectiveness as a marine fender plank without any added protectivecovering.

[0075] The composite cushion beam 10 is chemically inert, so it can lastindefinitely. It does not react with sea water, is corrosion free, issubstantially immune to the effects of light, is not bothered by mostpetroleum products, and is not subject to dry rot. Because it can bemade with recycled plastic, it is an environmentally sound investment.

[0076] Although the present invention has been described in considerabledetail with reference to certain preferred version thereof, otherversions are possible. For example the main rods 16 can be formed havinga flattened or elongate cross-section that is preferably oriented tofacilitate forming the connections with the transverse rod elements 18.Therefore, the spirit and scope of the appended claims should notnecessarily be limited to the description of the preferred versionscontained herein.

What is claimed is:
 1. A composite beam comprising: (a) a framecomprising: (i) a plurality of longitudinal main rod members, at leastthree of the main rod members being spaced laterally in differentcorresponding directions relative to a longitudinal axis of the frame;and (ii) a plurality of transverse elements, each transverse elementbeing rigidly connected between a spaced pair of the main rod members,at least three of the main rod members being connected to at least twoothers of the main rod members by at least some of the transverseelements; and (b) a resilient plastic body member encapsulating theframe, the plastic body having a nominal cross-sectional area of atleast 50 square inches.
 2. The composite beam of claim 1, wherein theplastic body forms an elongate cushion surface, the beam having anoverall thickness between the cushion surface and an opposite surface ofthe beam, the cushion surface being spaced from the frame by not lessthan 10 percent of the overall thickness.
 3. The composite beam of claim1, wherein at least some of the transverse elements are shear panels. 4.The composite beam of claim 3, wherein the shear panels compriselaterally spaced first and second sets of longitudinally spaced shearpanels, the panels of each set being bonded between a pair of the mainrod members.
 5. The composite beam of claim 4, wherein the first set ofshear panels is connected between a first pair of the main rod membersand the second set of shear panels is connected between a second pair ofthe main rod members.
 6. The composite beam of claim 5, wherein theplurality of main rod members includes respective third and fourth pairsof the main rod members, the first set of shear panels being furtherconnected between the third pair of main rod members opposite the rodmembers of the first pair, the second set of shear panels being furtherconnected between the fourth pair of main rod members opposite the rodmembers of the second pair.
 7. The composite beam of claim 3, wherein atleast some of the shear panels have openings and/or notches formedtherein, the body member having portions external to the cage frameintegrally joined through the openings and/or notches with portions ofthe body member within the frame for enhanced structural integrity ofthe body member.
 8. The composite beam of claim 1, wherein the main rodmembers and the transverse elements form a cage truss.
 9. The compositebeam of claim 1, wherein the main rod members and the transverseelements are each spaced at least 0.5 inch within an outside contour ofthe plastic body.
 10. The composite beam of claim 1, wherein the mainrod members are selected from the group consisting of formed steelreinforcing bars, formed nickel alloy reinforcing bars, fiberglassreinforcing bars, and carbon fiber reinforcing bars.
 11. The compositebeam of claim 10, wherein at least some of the transverse elements areselected from the group consisting of formed steel reinforcing bars,formed nickel alloy reinforcing bars, fiberglass reinforcing bars,carbon fiber reinforcing bars, plastic dowels, wooden dowels, steelplates, and fiberglass panels.
 12. The composite beam of claim 1,wherein the main rod members have a nominal diameter of betweenapproximately 2 percent and approximately 6 percent of a nominal outsidecircumference of the plastic body.
 13. The composite beam of claim 12,wherein the plastic body sealingly surrounds the cage frame, having athickness over each of the main rod members and the transverse elementsbeing not less than approximately 4 percent of the nominal outsidecircumference of the plastic body.
 14. The composite beam of claim 12,wherein the outside circumference of the plastic body is approximately48 inches, and the diameter of the main rod members is approximately 1 ¼inch.
 15. The composite beam of claim 12, wherein the plastic body isrectangular in cross-section.
 16. The composite beam of claim 15,wherein the plastic body is square in cross section.
 17. The compositebeam of claim 1, wherein the plastic body substantially fills the spaceoccupied by the frame.
 18. The composite beam of claim 1, wherein theplastic body consists of a main polymeric component and an additivecomponent, the main polymeric component consisting of low-densitypolyethylene of which at least 60 percent is linear low densitypolyethylene, the additive component including an effective amount of anultraviolet inhibitor.
 19. The composite beam of claim 1, furthercomprising an attachment structure defining a spaced plurality ofattachment elements connected to plural spaced apart locations of theframe.
 20. An installed fender assembly comprising a plurality ofcomposite beams according to claim
 1. 21. A method for forming acomposite beam, comprising: (a) providing a plurality of elongate mainrod members; (b) providing a plurality of transverse elements; (c)rigidly securing opposite portions of each of the transverse elementsbetween a laterally spaced pair of the main rod members such that atleast three of the main rod members have pluralities of the transverseelements projecting therefrom in at least two directions havingcomponents perpendicular to the respective main rod members to form acage frame; and (d) encapsulating the cage frame in a plastic body. 22.The method of claim 21, wherein the rigidly securing is further suchthat at least some of the transverse elements are rod segments orienteddiagonally such that the main rod members and the transverse elements inplanes of the diagonally oriented rod segments are loaded primarily intension and compression in response to bending and shear loading of theresulting cage truss.
 23. The method of claim 21, wherein at least someof the securing is by welding.
 24. The method of claim 21, wherein atleast some of the securing is by forming joints of reinforced epoxyresin.
 25. The method of claim 21, wherein the rigidly securing isfurther such that at least some of the transverse elements are shearpanels such that the main rod members are strained primarily in tensionand compression in response to bending and shear loading of theresulting cage truss.
 26. A method for forming a composite beam,comprising: (a) rigidly securing a spaced plurality of main rod membersto opposite edge regions of a first longitudinally spaced array of shearpanels to form a first frame portion; (b) rigidly securing a spacedplurality of main rod members to opposite edge regions of a secondlongitudinally spaced array of shear panels to form a second frameportion; (c) locating respective portions of the first and second frameportions in laterally spaced relation; (d) rigidly securing alongitudinal array of transverse elements between the first and secondframe portions to form a cage frame; and (e) encapsulating the cageframe in a plastic body.
 27. The method of claim 26, wherein theencapsulating comprises: (a) providing an injection mold having anelongate cylindrical cavity; (b) loading the mold with the welded cageframe; (c) centering the welded cage frame within the mold; (d)injecting a polymeric composition into the mold thereby covering thecage frame; and (e) cooling the mold to form the structural plasticmember.
 28. The method of claim 27, wherein the injecting comprisesformulating the polymeric composition to consist of low densitypolyethylene, at least 60 percent of the polymeric composition beinglinear low-density polyethylene.
 29. The method of claim 26, furthercomprising bonding a plurality of fastener attachments to the cage frameprior to the injecting.